1. Field of the Invention
The present invention relates primarily to a power source apparatus provided with a high capacity array of batteries to output both high voltage and high current.
2. Description of the Related Art
A power source apparatus with both high output voltage and high output current has many batteries connected in series to increase the output voltage. By combining many battery cells in modular form, solutions that are flexible with respect to different voltages and currents become possible. Battery cells can be formed into units or modularized to form battery packs. Power source apparatus that can connect a plurality of battery packs in parallel have previously been developed by the present applicant and others (refer to Japanese Laid-Open Patent Publication 2006-149068).
These types of power source apparatus contain protection circuitry to protect the battery cells from conditions such as over-charging and over-discharging. Protection circuitry protects the battery cells by action such as opening a circuit breaker when an abnormal condition is determined. For example, an abnormal condition can be battery pack charging or discharging current in excess of a threshold value, or detection of voltage in a battery cell, which makes up a battery pack, above an upper limit threshold or below a lower limit threshold.
However, when a plurality of these modularized battery packs are put together to form a power source apparatus, each module houses protection circuitry. As a result, protection circuitry is duplicated, and that duplication is wasteful from the perspective of cost and space. Further, since the protection circuitry in each module operates independently, response to an abnormal condition can result in interference or contradiction when many modules are used in combination. Contending with these different judgment results generated by many modules for a given abnormality is problematic.
The present invention was developed considering these types of prior art problems. Thus, it is a primary object of the present invention to provide a power source apparatus that is formed by combing a plurality of modules and has battery protection circuitry capable of operating with a high level of reliability.